package com.scau.jansing.thread.first.latch;

import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

/**
 * Created by jansing on 2015/12/23.
 */
public class CountDownLatchDemo {
    static final int SIZE = 100;
    public static void main(String[] args){
        ExecutorService exec = Executors.newCachedThreadPool();
        CountDownLatch latch = new CountDownLatch(SIZE);
        for(int i=0; i<10; i++){
            exec.execute(new WaitingTask(latch));
        }
        for(int i=0; i<SIZE; i++){
            exec.execute(new TaskPortion(latch));
        }
        System.out.println("Launched all tasks");
        exec.shutdown();
    }
}

class TaskPortion implements Runnable{
    private static int counter = 0;
    private final int id = counter++;
    private static Random rand = new Random(47);
    private final CountDownLatch latch;

    TaskPortion(CountDownLatch latch) {
        this.latch = latch;
    }
    @Override
    public void run() {
        try{
            doWork();
            latch.countDown();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    public void doWork() throws InterruptedException {
        TimeUnit.MILLISECONDS.sleep(rand.nextInt(2000));
        System.out.println(this + " completed");
    }
    @Override
    public String toString(){
        return String.format("%1$-3d ", id);
    }
}

class WaitingTask implements Runnable{
    private static int counter = 0;
    private final int id = counter++;
    private final CountDownLatch latch;
    public WaitingTask(CountDownLatch latch) {
        this.latch = latch;
    }

    @Override
    public void run() {
        try{
            latch.await();
            System.out.println("Latch barrier passed for " + this);
        } catch (InterruptedException e) {
            System.out.println(this + " interrupted");
        }
    }
    @Override
    public String toString(){
        return String.format("WaitingTask %1$-3d ", id);
    }
}

